Obesity, sedentariness and aging are known to be associated with hyperlipidemia, glucose intolerance, and altered sympathoadrenal responsiveness. In order to examine the interrelationship of age, adiposity, and physical fitness to endocrine-metabolic function, a study was designed to examine glucose and lipid metabolism and sympathoadrenal function in obese sedentary men aged 45-85 years at entry into the study and again after either weight reduction or aerobic training. The three areas of endocrine-metabolic function being studied are: 1) glucose tolerance and insulin sensitivity studied by the euglycemic clamp technique; 2) lipoprotein metabolism as assessed by measuring lipoprotein lipid profiles, HDL subspecies levels and lipoprotein lipase activity in postheparin plasma and adipose tissue; and 3) sympathoadrenal responses to isometric exercise (handgrip), upright posture, oral glucose challenge, and hyperinsulinemia during a euglycemic clamp. At this time, 48 participants have completed the baseline metabolic studies and have been randomized to either the weight reduction or aerobic exercise training intervention groups. The baseline studies indicate that these men have low levels of physical fitness, 25-30% have impaired glucose tolerance, and many are insulin resistant and have low plasma levels of HDL cholesterol. Twelve subjects have completed the weight loss program and undergone repeat metabolic testing. With weight loss there was a significant improvement in a number of the metabolic parameters with no change in their maximal aerobic capacity. Two subjects are trained and are now being retested. There are currently 14 subjects in the weight loss group and 20 in the exercise training program. They should be ready for retesting during the next 6-8 months. An additional 20 subjects are in the initial phases of baseline testing.